By talking to him and asking him if there's any other things you can unlock, he will reveal that for 100 golden nuggets and a level 72 Mining level (not boostable) you can use the upper section of the Motherlode Mine. For 200 golden nuggets you can get the larger sack upgrade, increasing the capacity of the sack at the end of the cleaning machine from 81 to 162.

Treasure Trails

Percy is the solution to the hard anagram clue: COPPER ORE CRYPTS. He will then give you a challenge clue; the answer is 12.

Trivia

According to a Reddit post by former Mod Reach, this character draws inspiration from Stinky Pete, the prospector in Toy Story 2. The character's overall appearance and examine text are references to this.